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CR2032 Battery Holder With Switch

Introduction: CR2032 Battery Holder With Switch

The purpose is to create a CR2032 battery holder water/dirt resistant with a power switch, using low cost or recycled material.
In this way the battery can be easily installed near the hub of a bicycle wheel to feed LED lights fixed on spokes or on a crash helmet (I will illustrate these applications in other Instructables).
I used a very common plastic (PE) cap of a water bottle that has an inner room that fits the dimensions of a CR2016 or CR2025 up to a CR2032, and the back of another cap to seal the battery inside, welding the PE parts with the tip of a soldering iron.
The switch was pinned on the side of the main cap and electrical contacts to the battery were made with jagged washers and some pieces of a PC flat cable for the wiring.
The outer rim that results can be used to obtain at will buttonholes/holes to install the kit on the final destination using plastic tie wraps or screws.

Step 1: Some of the Things Used

The material used are a micro switch, a CR2032 Battery and two water bottle PE caps.
It is better to use caps for still water because they don't have reinforcement ribs on the inside or bulges as the ones for sparkling beverages have. This reinforcement is not needed here because of the small weight of the battery (about 4 grams) and mainly not to waste room inside the housing.
You can chose the colour of the caps following your personal taste, but since you will have to connect pieces together, it is advisable to make a welding test to see if the colour charge doesn't give problems.
For my personal choice and to avoid any issue I used white-transparent caps as shown in the picture.

Step 2: Shaping the Plastic Cap for the Switch and Tie Wraps

The switch will be fixed on the side of the cap.
Remove with scissors all the threaded side of the cap up to the base except a convenient part to fit the switch.
The width of this tab should be at least 2-3 mm wider than the switch to allow its case pins to be folded sideways, the exceeding material could be removed later.
Refine the scissors cut with a sharp cutter for a better look.

Step 3: Drill a Hole for the (-) Negative Wire

Drill a hole of convenient diameter on the vertical rim for the wire to go from inside to outside the battery housing.
As I used a piece of an old PC flat cable the diameter of the hole will be about 0.8 mm.
It's advisable to keep this hole as small as possible to improve the sealing once the wire is inside.
Actually the plastic coating of the wire should have a little interference with its hole.
To improve the electrical contact with the battery I welded a jugged washer to one side of the wire.

Step 4: Installing the Negative Wire and the Switch

Bend and distort the tab that was kept from the side of the cap to make it as straight as possible to fit the switch, you can use small pliers, PE is easy to deform plastically.
Trace and drill 0.8 mm diameter holes on the tab for the 5 pins of the switch .
Insert all the switch pins and fold sideways the outer ones along with the one not used. This will guarantee mechanical strength to the bounding.
Insert the wire in its hole so that the washer is placed at the centre of the housing.

Step 5: Connect the (+) Positive Wires

Weld the battery (+) positive contact wire on the middle pin of the switch and the output on the other.
Now you are ready to insert the battery inside the housing.

Step 6: Make the Cover to Seal the Battery

To make the sealing cover for the battery take another plastic cap and remove anything but the inner rim and its bottom .
Trim the rim so it is about 1 mm high from its bottom. Some little material in excess will be useful in the welding phase.

Step 7: Welding the Cover

Put the parts in place and hold them in a vice.
Then with the tip of a soldering iron melt the material in the junction blending both sides.
The temperature of the iron should be enough to melt PE but not to burn it.
Be careful to clean the tip of the soldering iron frequently to prevent any material to burn and produce nasty fumes.
Use a fume extractor or do it in a open space.
Once the PE is melted locally you can apply some pressure with a cold object (e.g. a flat screwdriver) to help the flow of the material and revome holes and cavities.

Step 8: Remove Cold Drops From the Welding

Scrape the welding surface with a sharp cutter to remove cold drops and if necessary use the soldering iron again where the welding was not good enough.
Test the switch and the battery with a multimeter and if everything is fine you are ready to use it for your applications.
The outer edge will provide the fixing to other parts using screws, tie wraps and so on, buttonholes/hole can be obtained in the appropriate positions.
I use tie wraps to fix this battery next to the hub of my bicycle wheels to feed the high luminosity LED lights I have installed on the spikes for night visibility and safety. I also put white reflective tape on the battery holder to use it as a reflector.

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13 Comments

Neat idea - The natural springiness of the crinkle washers and the small amount of flex in the caps keeps the connections tight. I could well be using this idea. Just for info, a CR2032 battery has a capacity of around 200 - 220 mAh so you can work out your expected runtime from that. (e.g. 10 hours @ 20mA, 20 hours @ 10mA etc.)

Yes, your analysis is quite correct: actually the thickness of the washers requires some flex of the caps when welding them and this is helpful to keep the connections tight! :-) Before of this solution I just wrapped the battery and the connections with tape and then attached it to the spikes of the wheels using duct tape. Not a robust solution because many times I had to squeeze the battery with my fingers to make the connections work again and sometime with poor results. I also tried commercial battery holders but after wrapping them with tape to protect from water the result was too thick and cumbersome for my bicycle. Also I still had the problem where to install the switch. Then I came up with this solution that matches better my requirements. Yes, I knew about the capacity of the CR2032 batteries, I am happy with it since I am using them on my bicycle wheels to power LEDs since 7 years ago. I use the bicycle mainly with daylight and I switch the LEDs on only near sunset just to come home safely. So even if the calculated duration might seem short, however it may last many weeks or months and the replacement of the battery may become secondary to the sealing. I am glad that you are going to use this idea, a friend of mine used it to put a LED light on the collar of his dogs because he likes to play with them in the fields when dark but he needs some help to see them where they run! :-)

I just found this and plan to apply it to another project I found on here...hopefully this makes sense: a slight twist (pun intended) I plan to try is the sever the top of a bottle whose ID of the bottle opening is adequate for the battery. You can then plastic-weld a cap to seal the open side and once you have completed the remaining construction, you could screw the lid on/off to change batteries. I'll post again with photos if/when I actually get around to it.

The screw of the cap could be used to switch power on/off . To avoid the cap to fall when not tightened (power off) you can use a pin fixed on the bottle screw and a corresponding buttonhole on the cap that allows the required angle from on to off position.

Yes, there is a simple way to replace the battery, you can use a sharp cutter and remove the cover along the welding. PE allows many cycles of heating and cooling without loosing much of its properties, so you can weld it again and again. If you don't require a perfect sealing but only to keep the battery in place you can instead spot weld the cover to make replacement easier. If the PE parts got damaged you can do new ones easily re-use all the other parts. Actually it is a long time that I use CR2032 batteries to power LED lights (2 on each wheel of my bicycle) and they last so many hours that their replacement wasn't an issue compared to their sealing.